How to modify your Genesis 2/3/Nomad etc.

This has been a long time coming. The Genesis/MegaDrive model 1 is easy to mod, and instructions for doing this have been available on the internet seemingly forever. The newer model system (And its variants) have never been as well documented. A few years ago Mark Knibbs recruited my help (or more accurately my wife's help, she did the hard stuff) to identify which pins were and were not grounded on a few chips inside the model 2 Genesis. We did, and never heard back from him on what he found. Apparently he solved the mystery, but never posted the results on his page. Mike G did, and that's where we found the results of a few people's hard work.

Using that meagre knowledge, applicable to only one system, I spent the better half of my afternoon putting it to good use. What follows are the results: modification data for not only the Genesis 2, but also the nomad, CDX, Genesis 3 and Laser Active. The Gen3 and LaserActive mods were more difficult - the information found earlier didn't apply. I spent twenty minutes staring at the PCBs from the Genesis and MegaDrive LaserActive modules looking for differences.


By Connecting Pin 107 of the 315-xxxx chip inside the Genesis 2 system to either Ground or +5v, you can select Japanese or North America as the system's territory. The same theory applies to pin 46 of the same chip: +5v is 60Hz and Ground is 50Hz.

Some important notes: There are three territory codes for every Genesis system: Japan, North America and Europe. There are two switches used to set these modes: PAL/NTSC and US/JP. Both US and JP are NTSC, so you can easily switch between them. Europe is PAL and US. There is no territory using PAL and JP as far as I know.

Also: Not all 315-xxx chips are created equal. I've been told, but cannot confirm, that doing this to a 315-5685 chip will not work and may cause damage. If you're modding a Genesis2, and the chip is anything but the 315-5685, check to ensure the pin you're changing is already connected to GND or +5v; if it's not there's a chance it's used for something else.

Also: Sega CD systems use a ROM that acts like a cartridge when no actual cartridge is detected. This ROM detects which mode your system is set to (US/JP/EU) and will or will not run depending on what it's programmed to accept. A Japanese CD system will not work on a US Genesis, unless the Genesis is set to JP mode.


A simple mod. As seen on our 50/60Hz Nomad Page the nomad is an easily modified beast. Here's a quick recap of the two jumpers and three modes:
[ Nomad Pack PCB Overview ]
[ Nomad Pack PCB Closeup ] [ Nomad Genesis Pack PCB Closeup ]

JP1 = US
JP2 = JP

Pioneer LaserActive

There are two stages to this mod. The first requires soldering a simple on/off switch to the location shown below. If you close this jumper, it's in JP mode. If you open it, it's US mode.
[ LaserActive Genesis Pack PCB Overview ]
[ LaserActive Genesis Pack PCB Closeup ]
R152 is the US/JP Jumper

This only affects CARTRIDGES - for CD games you must ALSO change the socketed EPROM. There is only once socketed chip, a 27C1024. Here are the ROM images:
Japanese ROM

It's a simple matter to program a 27C2048 EPROM to function as both US and Japanese depending on which bank is selected when you throw the switch connected to R152. Even if you don't reprogram your EPROM, you can still easily play cartridge games with only the jumper.

Genesis 3

Very easy mod. Unlike the other Model 2 units, this system uses a very different chip. Luckily, that makes our job a lot easier. Open it up and look for the location shown below.

[ Genesis 3 PCB Overview ]
[ Genesis 3 PCB Closeup ]

There are four jumpers,. The bottom two are the JP/US jumpers. The top two are assumed to be the 50/60 Hertz jumpers (assumed, because I have neither software nor hardware to test them). To switch between them simply move the jumper from one to the other location. A more ideal solution is a switch - you can easily tell which is the common point.

Mega Jet

Nothing new here. Same rule applies - find the chip shown, connect a wire to the pad shown (bottom jumper, left side) and remove the existing jumper on RO245. Run a wire around the PCB to the pin shown and presto - hold the MODE button on powerup to set the system to the other region.

Sega/JVC Wonder Mega 1

This only applies to the WonderMega 1 system from either JVC or Sega. Open the system up and remove the cartridge-side PCB. Be careful, there's a lot of things plugged into it. Flip it over, and locate the spot shown below. Remove the existing jumper on R177. Connect your switch to either jumper pad on the chip (right) side. Apply either +5v or GND and you've got a working import mod.

Sega CDX or MultiMega

If you're feeling adventurous, You can do this mod on your CDX/MultiMega. This tiny well-constructed beast hates people and taking it apart is a real pain in the ass. Once you do, the fun isn't over! You need to locate the 315-xxxx chip and then either figure out where the lines from them run to (not easy on a 4-ply PCB) or lift the pins and solder wires to them directly! Here's a recap of the rules:

By Connecting Pin 107 of the 315-xxxx chip inside the Genesis 2 system to either Ground or +5v, you can select Japanese or North America as the system's territory. The same theory applies to pin 46 of the same chip: +5v is 60Hz and Ground is 50Hz.

Good luck!

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